Process of refining petroleum oils



Patented Jan. 17, 1939 PROCESS OF REFINING PETROLEUM OILS LeoLiberthson, New York, N. Y., assignor to L.

Sonneborn Sons, Inc., a corporation of Delaware No Drawing. ApplicationOctober 2, 1934, Serial No. 746,516

10 Claims.

The object of the invention is to provide an improved method of refiningpetroleum oils and more especially, an improved method of preparing awhite medicinal oil.

5 In accordance with prior practice, white mineral oils are prepared bysubjecting a carefully selected fraction of a crude petroleum totreatment with large quantities of acid, usually fuming sulphuric acid,the quantity of acid required for 10 the preparation of the most highlyrefined medicinal oils being of the order of 75% or more by volume ofthe oil treated. By such processes the yield of final product in generaldoes not exceed 50% of the amount of the fraction used in its 15preparation, the remaining 50% comprising acid sludge which is ofrelatively little value. Furthermore the product or products obtainedhave less desirable physical characteristics than do products obtainedin accordance with this inven- 2 tion.

White mineral oils such as those used for medicinal purposes aresubstantially water-white viscous products which, in accordance with theprior practice, have been obtained by subjecting 25 a carefuly selectedfraction of a crude petroleum, as for example, a fraction from anapthenic crude, to a drastic acid treatment as aforesaid. Thistreatment, due to the large quantities of strong acid used, results inthe destruction of the less 30 stable constituents contained in the oil,which probably accounts for the high oil loss incident to suchtreatment. This loss is referred to as an oil loss since the portion ofthe oil which reacts with the acid to form a sludge is only 35 partiallyrecoverable, and even when recovered it is usable only as a low gradefuel oil which has a very low market value.

Furthermore, processes in accordance with the prior practice wherebywhite mineral oils are 40 produced, require the use of oils ofrelatively low viscosity due to the fact that if treatment of theheavier oils is attempted, much difliculty is encountered and inaddition high chemical and mechanical losses result.

45 I have discovered that a pure white medicinal oil may be obtained bytreating a viscous mineral oil such as a petroleum lubricating oildistillate,

with dichloroethyl ether to remove major components of the oil whichreact with sulphuric acid.

50 The oil, which still contains small amounts of reactable components,is then treated with sulphuric acid, and preferably with oleum, formingan acid sludge. The acid sludge is separated from the oil and the oil isfurther treated with di- 55 chloroethyl ether. The dichloroethyl etherextract is separated from the oil and the oil is then treated with astripping solvent such as an alcohol, acetone, etc. The extract isseparated from the oil and an inert gas such as air, nitrogen, etc., ispassed through the oil to remove re- 5 maining small amounts ofstripping solvent and dichloroethyl ether. If desired, the oil may begiven a slight alkali treatment to neutralize such minute traces of acidas may have survived the previous extractions. The oil may then be 111-tered to remove traces of dichloroethyl ether and a pure white medicinaloil is obtained.

This product is superior to medicinal oils heretofore obtained, and theyield is appreciably higher. Furthermore, as indicated above, only asmall amount of sulphuric acid or oleum is necessary in the treatment,because the major amount of naphthenic and unsaturated components of theoriginal oil, which are reactable with sulphuric acid are removed by thefirst dichloroethyl ether treatment.

The invention may be carried out by subjecting one volume of viscousmineral oil, such as a Pennsylvania petroleum lubricating oildistillate, preferably by countercurrent extraction, to the action oftwo volumes of dichloroethyl ether to separate the components reactableand nonreactable with sulphuric acid. The dichloroethyl ether extractdissolves out the naphthenic and unsaturated components which react withsulphuric acid, and the raiiinate comprises principally the mineral oilcontaining the parafllnic hydrocarbons. The lower dichloroethyl etherextract layer is separated from the upper oil rafflnate layer, and ifdesired, the oil may be further treated with dichloroethyl ether.Preferably, the original oil is extracted three times by countercurrentextraction with dichloroethyl ether, but I am not to be limited to anynumber of extractions.

The oil now contains about 10% of dichloroethyl ether in solution, andis treated with 20 to 30% of sulphuric acid, and preferably oleum. It isnot necessary to remove the dichloroethyl ether remaining in solutionand in fact, I regard its presence as highly desirable inasmuch as itfacilitates the action of oleum on the oil by removing the sulfonicacids as areaction phase as fast as formed, thus permitting the reactionto arrive at a greater degree of completion than if it were absent. Theconcentration of SO: in the oleum may range over considerable limits,although 20% oleum, viz., acid containing this percentage of S03 issatisfactory. The temperature of application of the acid is regulated inthe manner well known in the art, to produce the desired sulfonationreaction, and, in general, temperatures not exceeding 140 F. arepreferred.

If desired, the original mineral oil need not be given a preliminarytreatment with dichloroethyl ether, but such ether may be added to theoil up to its solubility limit, and the oil may then be treated witholeum. In this case, a larger amount of oleum will be required, but thesulfonation reaction will arrive at a greater degree of completion thanif no dichloroethyl ether were present.

The organic acids in the sludge may compose from 25 to 75% of the totalsludge, and while slightly soluble, if at all, in hydrocarbon oils, arehighly water soluble. The free acids in aqueous solution are dark greenin color and for this reason are generally referred to as "greenpetroleum sulfonic acids. The acids left in solution in the oil impart areddish color to the oil containing the same and for this reason aregenerally referred to as mahogany petroleum sulfonic acids. The oil mayalso carry variable amounts of the green petroleum sulfonic acids asfinely dispersed or mechanically suspended particles. The mahogany acidsare soluble in dichloroethyl ether and may be efficiently and easilyremoved by admixing dichloroethyl ether with the oil.

In the ordinary method of removal, these acids are first converted intosalts by neutralization, but in my process this neutralization is notnecessary and the free acids are extracted as such. For whileneutralization yields salts of both green and mahogany acids in amixture which is separable only with great difiiculty, direct extractionwith dichloroethyl ether permits the quantitative separation of thesetypes of acids by virtue of the fact that dichloroethyl etherprecipitates the green and dissolves the mahogany acids. This should bedone after the oil has been separated from the sludge formed on reactionwith sulphuric acid. The dichloroethyl ether is soluble in the oil tothe extent of several percent and it is therefore necessary to add thedichloroethyl ether in an amount which exceeds its solubility in theoil, thereby yielding a two layer system. The dichloroethyl ether formsa lower layer ranging from 5 to 25% by volume of the oil from which itseparates. In any case, it should not be necessary to use more than 50%by volume of dichloroethyl ether to produce a second liquid phase inorder to obtain the complete removal of the sulfonic acids, and sharpseparation into two layers. These limits are merely intended asillustrations and not in any way as restrictions on the scope of theinvention. The residual green sulfonic acids dissolved in the oil asstated above are not soluble in the dichloroethyl ether but arecoagulated by contact with it and are precipitated as completelydiscreet and easily removable sludge, which forms an intermediate layerbetween the oil and dichloroethyl ether layers. The oil soluble sulfonicacids, on the other hand, will be found to have passed almostexclusively into the lower dichloroethyl ether layer, and to have beenalmost completely removed from the oil. The lower layer is separatedfrom the oil and may, if desired, be treated to recover the mahoganyacids in usable form. If desired, extraction with dichloroethyl ethermay be carried out countercurrently a number of times, and I have foundthat about three extractions precipitate substantially all of the greenacids and extract substantially all the mahogany sulfonic acids from theoil.

The oil layer is then treated with a stripping solvent, which may be analcohol having not more than three carbon atoms, or other solvent havinga high vapor pressure and a boiling point of preferably not greater than80 C. The solvent should be miscible with the dichloroethyl ether butsubstantially immiscible with the oil, so that two well defined layerswill be formed. As examples of such stripping solvent may be mentionedmethyl alcohol, ethyl alcohol, propyl alcohol, acetone, methyl ethylketone, etc. The stripping solvent removes the dichloroethyl ether andany mahogany acids and other impurities which may be left in the oillayer. The stripping solvent extraction, if desired, may be carried outa number of times, as for example, by countercurrent extraction threetimes. In each case, the stripping solvent extract is separated from theoil before the next extraction.

After the last separation, the oil contains small amounts of strippingsolvent and dichloroethyl ether, and these may be removed by passing aninert yas through the oil. The inert gas, such as air, nitrogen, etc.,may be at ordinary temperatures or elevated temperatures. The inert gasremoves all of the alcohol and substantially all of the dichloroethylether and traces of the latter can be removed by treatment with anadsorbent material, for example, with adsorbent clay, etc. The claytreatment may be carried out in any suitable manner, as for example, byrunning the oil through a porous bed of fullers earth, or the like, in apercolation type of filter, or, by admixing the oil with fine adsorbentclay, and thereafter settling or filtering the same.

The pure, white medicinal 011 formed has a Saybolt viscosity at 210 F.of 390-400 and the yield is about 75%, as compared with a viscosity of335-350 and yields of about 50% with processes heretofore used. It issuperior to that ordinarily produced from a corresponding raw materialwith the amount of oleum necessary to convert it to a white medicinaloil, and in particular will be markedly superior in its resist ance tothe effect of prolonged exposure to light and/or to ultra violet light.There are no minute traces of oil soluble organic material in the oil,and these is substantially no objectionable odor, color, or taste uponexposure to natural or ultra violet light for prolonged periods.

I am not to be limited to any number of extractions with dichloroethylether or stripping solvent, nor to any volume of extracting substances.By stripping solvent as used in the specification and claims I mean analcohol having not more than three carbon atoms, or other solventmiscible with dichloroethyl ether and substantially immiscible with oil,and having a sufficiently high vapor pressure and low boiling point topermit removal by passing an inert gas through the oil.

I claim:

1. In the art of refining mineral oils, the step comprising ,treating aviscous mineral oil with fuming sulphuric acid under sulphonatingconditions of acid quantity and temperature in the presence ofdichloroethyl ether in amount sulfi- .cient to thereby formsimultaneously a first layer containing predominantly dichlorethyl etherand dissolved mahogany sulphonic acids, and a coagulated precipitatecontaining predominantly green sulphonic acids.

2. In the art refining mineral oils, the steps which comprise extractinga viscous mineral oil with dichloroethyl ether to dissolve from the oila substantial part oi the components thereof which react with sulphuricacid, separatingthe dichloroethyl ether from that portion of the oilwhich remains undissolved therein, and treating the undissolved portionof the oil with sulphuric acid under sulphonating conditions of acidquantity and temperature in the presence of the dichloroethyl ethersoluble in the oil to thereby form simultaneously a layer substantiallyfree from mahogany and green sulphonic acids formed by the acidtreatment and containing predominantly mineral oil and dissolveddichloroethyl ether, and an acid sludge containing mahogany and greensulphonic acids.

3. In the art 01 refining mineral oils, the steps which compriserepeatedly extracting a viscous mineral oil distillate withdichloroethyl ether to dissolve from the oil a substantial part of thecomponents thereof which react with sulphuric acid and separating thedichloroethyl ether layers from that portion of the oil which remainsundissolved therein, and treating the undissolved portions of oil witholeum under sulphonating conditions of acid quantity and temperature inthe presence of the dichloroethyl ether soluble in the oil to therebyform simultaneously a layer substantially free from mahogany and greensulphonic acids formed by the acid treatment and containingpredominantly mineral oil and dissolved dichloroethyl ether, and an acidsludge containing mahogany and green sulphonic acids.

4. In the art of refining mineral oils, the process comprisingextracting a viscous mineral oil with dichloroethyl ether to dissolvefrom the oil a substantial part of the components thereof which reactwith sulphuric acid and removing the dichloroethyl ether layer, treatingthe oil layer with sulphuric acid under sulphonating condi-- tions ofacid quantity and temperature in the presence of the dichloroethyl ethersoluble in the oil to thereby form simultaneously a layer substantiallyfree from mahogany and green sulphonic acids formed by the acidtreatment and containing predominantly mineral oil and dissolveddichloroethyl ether, and an acid sludge containing mahogany and greensulphonic acids, separating said acid sludge from said oil layer,extracting said oil layer with dichloroethyl ether and removing thedichloroethyl ether layer, treating the oil layer with a strippingsolvent, removing the solvent layer, and passing an inert gas throughthe oil layer so as to remove thereby stripping solvent anddichloroethyl ether dissolved in the oil.

5. In the art of refining mineral oils, the process comprisingrepeatedly extracting a viscous mineral oil distillate withdichloroethyl ether to dissolve from the oil a substantial part of thecomponents thereof which react with sulphuric acid and removing thedichloroethyl ether layers, treating the oil layer with oleum undersulphonating conditions of acid quantity and temperature in the presenceof the dichloroethyl ether soluble in the oil to thereby form a layersubstantially free from mahogany and green sulphonic acids formed by theacid treatment and containing predominantly mineral oil and dissolveddichloroethyl ether, and an acid sludge containing mahogany and greensulphonic acids, separating said acid sludge from said 011 layer,repeatedly extracting said oil layer with dichloroethyl ether andremoving the dichloroethyl ether layers, treating the oil layer with astripping solvent, removing the solvent layer and passing an inert gasthrough the oil layer so as to remove thereby the stripping solvent anddichloroethyl ether dissolved in the oil.

6. Process in accordance with claim 5 in which said stripping solvent isalcohol and in which the inert gas passed through said oil layer is air.

7. Process in accordance with claim 5 in which said stripping solvent isacetone and in which said inert gas passed through said oil layer is ar.

8. In the art of refining mineral oils, the proccess comprisingrepeatedly extracting a viscous 'mineral oil distillate withdichloroethyl ether to dissolve from the oil asubstantial part or thecomponents thereof which react with sulphuric acid and removing thedichloroethyl ether layers, treating the oil layer with oleum undersulphonating conditions of acid quantity and temperature in the presenceof the dichloroethyl ether soluble in the oil to thereby form a layersubstantially free from mahogany and green sulphonic acids formed by theacid treatment and containing predominantly mineral oil and dissolveddichloroethyl ether, and an acid sludge containing mahogany and greensulphonic acids, separating said acid sludge from said oil layer,repeatedly extracting said oil layer with dichloroethyl ether andremoving the dichloroethyl ether layers, treating the oil layer with astripping solvent, removing the solvent layer and passing an inert gasthrough the oil layer so as to remove thereby the stripping solvent anddichloroethyl ether dissolved in the oil, and treating said oil layerwith an adsorbent agent.

9. In the art of refining mineral oils, the process which comprisesextracting a viscous mineral oil distillate with dichloroethyl ether todissolve from the oil a substantial part oi. the components thereofwhich react with sulphuric acid, removing the dichloroethyl ether layer,treating the oil layer with a further quantity of dichloroethyl ether tofurther dissolve from the 011" components thereof which react withsulphuric acid, again removing the dichloroethyl ether layer, treatingthe oil layer with oleum under sulphonating conditions of acid quantityand temperature in the presence of the dichloroethyl ether dissolved inthe oil to thereby form simultaneously a layer substantially free frommahogany and green sulphonic acids formed by the acid treatment andcontaining predominantly mineral oil and dissolved dichloroethyl ether,and an acid sludge containing mahogany and green sulphonic acids,separating said acid sludge from said oil layer, treating the oil layerwith dichloroethyl ether, separating the dichloroethyl ether layer,treating the acid treated oil with a further portion of dichloroethylether, again removing the dichloroethyl ether layer, treating the oillayer with a stripping solvent, removing the solvent layer, treating theoil layer with a further portion of stripping solvent, again re movingthe solvent layer, and passing an inert gas through the oil layer so asto remove thereby the stripping solvent and dichloroethyl etherdissolved in the oil.

10. In the art of refining mineral oils, the proc: ess which comprisesextracting a viscous mineral oil distillate with dichloroethyl ether todissolve i'rom the oil a substantial part of the components thereofwhich react with sulphuric acid, removing the dichloroethyl ether layer,treating the oil layer with a further quantity of dichloroethyl ether tofurther dissolve from the 011 components thereof which react withsulphuric acid, again removing the dichloroethyl ether layer, treatingthe oil layer with oleum under sulphonating conditions of acid quantityand temperature in the presence of the dichloroethyl ether dissolved inthe oil to thereby form simultaneously a layer substantially free frommahogany and green sulphonic acids formed by the acid ;treatment andcontaining predominantly mineral oil and dissolved dichloroethyl ether,and an acid sludge containing mahogany and green sulphonic acids,separating'said acid sludge from said oil layer, treating the oil layerwith dichloroethyl ether, separating the dichloroethyl ether layer,treating the acid treated oil with a further portion of dichloroethylether, again removing the dichloroethyl ether layer, treating the oillayer with ethyl alcohol, removing the alcoholic layer, passing airthrough the oil layer so as to remove thereby alcohol and dichloroethylether dissolved in the oil, and treating said 011 layer with anadsorbent agent.

- LEO LIBERTHSON

